1. Field of the Invention
The present invention relates to a mobile terminal and a server in a navigation system for providing a vehicle with a travel route guidance, and more particularly to a mobile terminal and a server provided in a navigation system, in which the navigation function can be attained by use of an on-demand system through communications between the mobile terminal which is not equipped with a map database, and a server which is equipped with a map database.
2. Description of the Related Art
Conventionally, there have been disclosed various navigation systems of this kind so far, a case in point being the one disclosed in Japanese National Publication of the translated version No. 10-505420.
FIG. 1 is a schematic diagram showing the configuration of a conventional navigation system as disclosed in the above-mentioned National Publication. In the figure, numeral 1 denotes one of a number of mobile parts, numeral 2 denotes a fixed part, and numeral 3 denotes a cellular telephone network by which the fixed part 1 and the mobile part 2 are mutually connected to each other.
In the mobile part 1, numeral 10 denotes a mobile telephone such as a hand-free cellular telephone, numeral 11 denotes an audio output, 12 denotes an audio input, and 13 denotes a radio antenna. Numeral 14 denotes a DTMF (Dual-Tone Multi-Frequency) decoder for translating DTMF signals, numeral 15 denotes a GPS (Global-Positioning System) satellite receiver for obtaining the geographical position of the mobile part 1 within which the GPS receiver itself is provided, 16 denotes a DTMF encoder for encoding signals into DTMF signals, 17 denotes an interface controller for receiving signals from the DTMF decoder 14 and the GPS receiver 15, and also feeding signals to the DTMF encoder 16, numeral 18 denotes a loudspeaker for allowing the telephone 10 to be used for speech, and numeral 19 denotes a microphone used for the same purpose.
In the fixed part 2, numeral 20 denotes a DTMF decoder, 21 denotes a DTMF encoder, and 22 denotes an interface controller. Further, numeral 23 denotes a computer connected to the cellular telephone network 3 by way of the DTMF decoder 20 and the DTMF encoder 21, and also by way of the interface 22, and numeral 24 denote a number of servers configuring the computer 23. Numeral 25 denotes a geographical database accessed by each of these servers 24, numeral 26 denotes a database of messages, 27 denotes an input for updating the geographical database 25, and numeral 28 denotes voice messages generated by the computer 23 and transmitted to the cellular telephone network 3.
The operation of the conventional device is now explained as below.
Here, each one of the servers 24 within the computer 23 is allocated to each of the active mobile parts 1 by way of the cellular telephone network 3. The mobile part 1 obtains location information using the GPS receiver 15, and transmits the thus obtained information to the fixed part 2 together with a request for directions to a specified destination. In the fixed part 2, the corresponding server 24 relates the location information to its geographical database 25, obtains message information associated with the location from the message database 26, and transmits the information back to the mobile part 1.
The computer 23 may transmit messages in DTMF code, using the DTMF encoder 21, or it may generate voice messages which are transmitted through a voice output 28 to the cellular telephone network.
When the position of a vehicle (namely the position of the mobile part 1) is transmitted to the computer 23 by use of the DTMF signals, the computer 23 can provide a vehicle or a third person requesting it with information or route guidance.
First of all, at the start of journey, the driver of a vehicle in which the mobile part 1 is mounted requests a service by activating a predialled control on the mobile telephone 10. This service request is transmitted to the interface controller 22 in the fixed part 2 over the cellular telephone network 3. The interface controller 22 then allocates a free server 24 to answer the call and interrogate the GPS receiver 15 of the mobile section 1 to determine its geographical position. The longitude and latitude data values output from the GPS receiver 15 are translated into DTMF tone-pairs by the DTMF encoder 16 of the mobile 1.
The mobile telephone 10 couples this audio signal into its speech input path of the audio input 12, and the DTMF decoder 14 coupled to the loudspeaker 18 decodes the supervisory data in DTMF format coming back from the corresponding server 24 of the fixed part 2 to acknowledge the reception of location messages.
Further, the computer 23 in the fixed part 2, on one hand, can call the mobile part 1 which automatically answers to this call, and then provide its location using the DTMF signaling system, or on the other hand, can receive a call from the mobile part 1, which could include the DTMF encoded identity of the mobile part 1, and would also provide the vehicle location using the interface controller 17.
The server 24 then captures the geographical database 25 on the basis of the current position of the user, and identifies the area within which that current position falls. The server 24 also captures any permanent user-specific information such as the type of vehicle, which may be relevant for the route to be selected, for example, because of height or weight restrictions. The user may encode those requirements for current data, which are not permanent, but are specific to the present information request (in particular his destination) using the telephone keyboard of the mobile telephone 10 in respect to voice prompts. Note that in a preferred embodiment, however, the call is presented to a human operator for the capture of this data, and this allows the user to obtain assistance in identifying his desired destination to the system, and also allows to speak his requirements, keeping his eyes and hands free for driving.
The operator then remotely programs the interface controller 17 in the mobile part 1 with system data identifying the vehicle destination, for use in subsequent data update processes, and instigates the generation of the voice-given directions and instructions to the driver by a speech generation subsystem of the computer server 24 of the fixed part 2.
Position fixes may be performed at regular intervals such as every 2 minutes, or every kilometers. Alternatively, the fixed part 2 may request the mobile part 1 to send its next position after a specified interval or distance.
When the driver is following the route, further instructions can be sent automatically as the driver enters each new area, the driver can be alerted if the route has been left or if any new traffic problems have been detected that will affect the individual driver.
This system is arranged such that when this system locates a mobile part entering an area having a message defined for it, for example, the next turn instruction (or an error message in the case where the mobile part 1 has gone off the selected route), that message is transmitted. This system may also be arranged to transmit messages to users other than the mobile part 1 in question, for example, to monitor the progress of valuable cargoes.
In the conventional navigation system as configured above, the mobile terminal (mobile part 1) is a device for timely providing a user with the information required for him to reach his destination by informing the location information of himself at least in each area to the server 24 of the fixed part 2, so that even in the case where no new information from the server 24 is required, each time he enters a new area, communications for obtaining necessary information for reaching the destination are performed, resulting in an increase in the total communication traffic.
Further, nothing about improving the method for a user to inform his destination to the server 24 of the fixed part 2 is talked about.
Note that the navigation system, in which a mobile terminal is not equipped with a map database but can carry out the navigation function by obtaining the map database through communications, is also disclosed in another document, namely Japanese Patent Application No. 7-320196 and the like. The navigation system in this document is the one that the location information obtained through the GPS received in the mobile terminal side is transmitted to the center (server) by way of a PHP terminal, and the center sends back the map data and traffic information based on the location information.
However, in this document, although the method for downloading the map data and the traffic information by way of a PHP terminal at the mobile terminal side is disclosed, neither concrete procedures for the downloading operation nor the way they are used is explained at all.
Accordingly, the present invention has been proposed to solve the problems aforementioned, and it is an object of the present invention to provide a navigation system which is capable of suppressing the frequency of communications between a mobile terminal and a server into a minimum level, and carrying out the navigation function using an on-demand system, wherein the mobile terminal is not equipped with any map database.
The present invention relates to a mobile terminal in a navigation system, which comprises a receiving means for receiving a first or a second recommendable travelling route data transmitted by way of a communication line, a location detection means for detecting the location of the mobile terminal itself, a comparing means for comparing the first or second recommendable travelling route data with a location detected by the location detection means, an indication means for indicating a direction to which the user should move on the basis of the result of the comparison made by the comparing means, and a new route requesting means for transmitting a request for a new second recommendable travelling route data to the communication line on the basis of the result of the comparison. Due to this construction, an on-demand navigation function with minimum frequency of communications is made possible.
The mobile terminal according to the present invention further comprises a transmission means for transmitting the location information and the destination information of itself to the communication line as a first condition. Due to this construction, setting of several points by way of which it travels is also made possible.
The mobile terminal according to the present invention further comprises a return indication means, which, in the case where a deviation of its location from the recommendable travelling route is detected on the basis of the result of the comparison executed in the comparing means, indicates the direction in which the nearest recommendable travelling route resides to the user. Due to this construction, returning to the guide route is made possible.
The mobile terminal according to the present invention comprises a return indication means, which, in the case where a deviation of its location from the recommendable travelling route is detected on the basis of the result of the comparison conducted in the comparing means, indicates the direction reverse to the recommendable traveling route after the deviation to the user. Due to this construction, returning to the guide route is made easier.
The mobile terminal according to the present invention further comprises a storage means for storing the data received through the communication line, a processing means for sequentially processing the data received through said communication line, a memory monitoring means for monitoring as to whether or not the summed amount of the memory area which has been made available after the completion of processing conducted by the processing means and unused memory area is substantially great, and a continued data requesting means, which, in the case where the result of the monitoring is substantially great and it is indicated that the received data contains a continued data, transmits a request for transmission of the continued data to the communication line. Due to this construction, an overflow of the memory can be automatically prevented.
The mobile terminal according to the present invention further comprises a data amount informing means for transmitting a notification of the amount of data storable in the memory to the communication line, in advance of receiving data by way of the communication line. Due to this construction, an overflow of the memory can be automatically prevented.
The mobile terminal according to the present invention further comprises an interruption requesting means, which, in the case where the result of the monitoring conducted by the memory monitoring means has become small during the data reception by way of the communication line, transmits a request for interruption of the data transmission to the communication line. Due to this construction, an overflow of the memory can be automatically prevented.
The present invention relates to a server in a navigation system, which comprises a request receiving means for receiving the starting point information and the destination information transmitted by way of the communication line as a condition, a route extracting means for extracting a recommendable travelling route in accordance with the condition received by the request receiving means, a transmission means for transmitting the recommendable travelling route by way of the communication line, and a destination setting information transmission means for transmitting destination setting information to the mobile terminal sequentially in the order of upper to lower layers, in response to the request received by way of the communication line. Due to this construction, the memory capacity required for setting of the destination can be made small.
The server according to the present invention further comprises a condition receiving means for receiving the condition for data transmission and a data-storage use memory amount information, both transmitted through the communication line, a processing means for carrying out processing on the basis of the condition for data transmission, a transmission means for transmitting the result of the processing conducted by the processing means, a data amount limiting means for limiting the amount of data to the level below the data storage-use memory amount information, and a continued information adding means for adding the information indicating that there exists continued data to the data to be transmitted to the communication line. Due to this construction, an overflow of the memory at the mobile terminal side can be automatically prevented.